Dear Cyril,
Thank you for your kind reply. My concern is that if I want to do an
"optimized VBM" by creating my own template, will the excessive number
of normal control bias the normalization process and the result by
having high weighting in my own template?
Regards,
Deqiang
Deqiang Qiu
Department of Diagnostic Radiology
The University of Hong Kong
Rm 406,Blk K,
Queen Mary Hospital
Pokfulam Road,
Hong Kong
Tel: (+852) 28553307
Fax: (+852) 28551652
-----Original Message-----
From: cyril pernet [mailto:[log in to unmask]]
Sent: 2006Äê6ÔÂ26ÈÕ 18:57
To: dqqiu
Subject: Re: [SPM] How to choose control subjects?
Hi there,
> Dear SPMers,
>
> We are carrying out a study to investigate possible structural
> difference in Asperger syndrome (ASD) and high functioning autism(HFA)
> using SPGR and DTI imaging.
>
> We have scanned 6 ASD and 7 HFA patients and have a pool of control
> subjects. In order to perform SPM, I need to select control subjects.
> But I¡¯m confused on different options:
>
> 1. select 13 control subjects , matching for age and gender for each
> patients
>
> 2. select 6(or 7)subjects with roughly similar age and gender
> distribution as ASD and HFA patients.
>
> It seems to me option 1 is better, but what model shall I use, ANOVA
> or ANCOVA(control for age and gender)?
>
I think the more the better .. take all your subjects and use a multiple
regression model.
Y = gp1+gp2+gp3+age+gender
Y = all your scans
gp1 = controls [11111111111110000000000000]
gp2 = ASD [00000000000001111110000000]
gp3= HFA [00000000000000000001111111]
age [xxxxxxxxxxxxxxxxxxxxxxxxx]
gender = 1 or -1
you will have a better estimate of the data in normals and therefore the
patient comparison should be more right ..
i don't really know about DTI but in VBM the total volume is also
entrered to control the global effect ..
hope it helps
best
cyril
> I really appreciate any input!
>
> Best Wishes!
>
> Sincerely yours,
>
> Deqiang Qiu
>
> Department of Diagnostic Radiology
>
> The University of Hong Kong
>
> Rm 406,Blk K,
>
> Queen Mary Hospital
>
> Pokfulam Road,
>
> Hong Kong
>
> Tel: (+852) 28553307
>
> Fax: (+852) 28551652
>
--
Pernet Cyril, PhD
Center for Cognitive Neuroimaging
Voice Neurocognition Laboratory
Department of Psychology
58 Hillhead Street
University of Glasgow
Glasgow G12 8QB
Scotland
[log in to unmask]
http://vnl.psy.gla.ac.uk/
tel: +44 (0)141 330 4965
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